فهرست مطالب مجتبی زادعلی محمدکوتیانی

In this study, Al-surface composite reinforced by in-situ formed  and  aluminide particles was fabricated by using friction stir processing (FSP). A rolled AA 3003-H14 aluminum alloy sheet and equal proportion of Zirconium and Titanium metal powders as reinforcement were used to fabricate Al-surface composite. Six FSP passes were applied to improve the distribution of reinforcing particles. Microstructural examinations were performed using scanning electron microscopy (SEM) and phase analysis was done by an X-ray diffraction (XRD) technique. Microstructural investigation revealed that due to the solid state chemical reactions,  and  aluminides have formed at the interface between the metal powders and the aluminum alloy matrix. Formation of these aluminides with in the span time of less than 40 s, was attributed to the activated thermomechanical condition induced by FSP. The effective Gibbs free energy change of formation ( ) model was used to thermodynamically predict the aluminide phase formation at the interface between the matrix and the reinforcing metal particles. The results of prediction, matched well with the experimental observations.

In this article, in-situ formed hybrid surface composite of Al 3003/Al3Zr + Al3Ti was fabricated by friction stir processing (FSP). A rolled Al 3003-H14 aluminum alloy sheet and zirconium and titanium metal powders were used as reinforcements and six passes of FSP were applied. Then, FSPed samples were subjected to annealing heat treatment at 500 ºC for 4 hours. Wear behavior and the hardness of the base metal as well as FSPed samples before and after annealing was measured. Microstructural observation was performed using optical (OM) and scanning electron microscope (SEM), and phase formation was identified with X-Ray diffraction (XRD). Microstructural examination revealed that applying the FSP, resulted in fine and equiaxed grains with more uniform distribution of reinforcing particles. It was also observed that chemical reaction occurred at the interface between the aluminum matrix and the metallic powders, to form aluminides of Al3Zr and Al3Ti. The post annealing heat treatment activated these solid state reactions and more aluminides were formed. It was also found that, the maximum hardness and wear resistance were obtained by the FSPed and annealed hybrid composite sample.

In this research, an in-situ hybrid composite reinforced by Al3Zr and Al3Ti aluminide particles was fabricated by friction stir processing (FSP). The base metal was in the form of a rolled Al 3003-H14 alloy sheet, and zirconium and titanium metal powders were used as the reinforcements. Six passes of FSP were applied. Tensile strength and hardness of the base metal, as well as FSPed samples before and after applying heat treatment, were determined. Microstructural examinations were performed using optical and scanning electron microcopy (SEM), and phase formation was identified by X-Ray diffraction. Microstructural examination revealed that by applying FSP, the prior large and elongated grains of the base metal were converted to the fine and equiaxed grains. It was also observed that chemical reactions occurred at the interface between the aluminum matrix and the metallic powders, forming in-situ aluminides of Al3Zr and Al3Ti. The post annealing heat treatment activated these solid state chemical reactions and more aluminides were formed. It was also found that the heat treated hybrid composite possessed the highest tensile strength and hardness values. The tensile strength in such samples reached 195 MPa, as compared to 110 MPa of the base metal.